Abstract - Effect of liming and its association with fertilization on the biogeochemical cycle of nutrients in a declining spruce stand (Picea abies Karst) in the Vosges (France). The forest decline observed in the 1980s showed a complex interaction between biological, edaphic, climatic and silvicultural parameters. The effects of the edaphic constraints were studied using in situ fertilization experiments, which demonstrated both the origin of some of the forest decline symptoms observed on spruce stands (Picea abies Karst) in the Vosges and the efficiency of the treatments applied. Liming restored the green growth and foliation of severely declining trees within 2 years independently of whether it was associated with complete fertilization (NPK). A detailed quantitative study of the mineral function of a spruce ecosystem which reacted positively to liming was set up in an experiment situated at Le Col du Bonhomme (Vosges). The soil is very acidic and its current geochemistry is dominated by nitrate and aluminium. Acidification is still an active process and the soil cannot neutralize acidity from external (atmospheric input) or internal origins. This acidity must be neutralized at depth in the sub-soil since the water in the catchment stream is neutral. Input-output budgets, even if they were not very accurate, always showed a Mg deficit whatever the time-scale considered (seasonal, yearly or over several years). This element is often cited as the cause of forest decline. Liming neutralized the soil acidity, particularly its Al component, and increased the Ca and Mg tree nutrition of the trees; nitrates decreased in the gravitational solutions of the liming treatment. Addition of fertilizers to liming, which did not clearly increase tree health and accelerated the depletion of Ca and Mg caused by liming, did not seem suitable in this situation. This experiment demonstrates clearly the role of edaphic parameters in this particular case of forest decline.